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osanseviero Group Title

I need to write a program that that prints the longest substring of s in which the letters occur in alphabetical order. For example, if s = 'azcbobobegghakl', then your program should print beggh How should this start?

  • one year ago
  • one year ago

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  1. e.mccormick Group Title
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    hmm... well, you could look at each character and see if it is <= the next. Count how many are, then make a sub string based on that. The issue is when to discard it if you find a larger string.

    • one year ago
  2. e.mccormick Group Title
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    azcbobobegghakl az alphabetical, but len 2. zc bad cb good, but not loneger cbo good, 3, drop the 2. ob bad bo good, but not loneger ob bad be good, but not loneger beg good, but not loneger begg good, loneger drop the 3 beggh good, loneger drop the 4 ha bad ak good but not longer akl good but not longer

    • one year ago
  3. e.mccormick Group Title
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    That is basically what it would do. Now for the how, use ifs and boolian comparisons.

    • one year ago
  4. osanseviero Group Title
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    so i keep creating substrings and comparing lengths, and depending on their lengths i will keep the largest one

    • one year ago
  5. e.mccormick Group Title
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    Well, you only need two bufer strings. The longes one as the answer and the now being worked on one. If the now worked becomes longer than the answer, replace the answer. >>> 'a'<'b' True >>> 'c'<'b' False >>>

    • one year ago
  6. osanseviero Group Title
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    How can I compare it with values from before?

    • one year ago
  7. e.mccormick Group Title
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    Testing each character as you go will let you decide if it is time to reset the buffer string or to add to it.

    • one year ago
  8. osanseviero Group Title
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    I need to rest.I will come back in some hours

    • one year ago
  9. e.mccormick Group Title
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    OK. This should give you something to start with. You can see what it would do and some info on how. Work with that and see how far you get.

    • one year ago
  10. osanseviero Group Title
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    In human talking, this would be done with this: 1. Take the first character 2. Save it. 3. Take the second character. 4. Compare them Option 1: a. If first character is bigger than the second one, FALSE statement, continue with first character as the substring. b. If first character is smaller, TRUE statement, new substring is first character + second one. 5. Repeat

    • one year ago
  11. osanseviero Group Title
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    But this would just work for a continued string...I dont know how it would be done for a new substring

    • one year ago
  12. e.mccormick Group Title
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    Well, if the first character is bigger, then you want to reset or erase the buffer string. If it is smaller, then you want to add it to the buffer string.

    • one year ago
  13. e.mccormick Group Title
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    And after every time through those, you want to see if the buffeer string is longer than the answer string. If so, replace the answer string with the buffer string.

    • one year ago
  14. osanseviero Group Title
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    Why does this give a number as an answer? s=raw_input("Enter a word: ") buffer="" for i in range(len(s)-1): if s[i]<=s[i+1]: buffer=str(i)+str(i+1) if s[i]>=s[i+1]: buffer=buffer print("Longest substring in alphabetical order is: " + str(buffer))

    • one year ago
  15. e.mccormick Group Title
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    |dw:1382852135152:dw|

    • one year ago
  16. e.mccormick Group Title
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    buffer=str(i)+str(i+1) buffer=str[i]+str[i+1] You need to use [ ] for string arrays. And you only want to work on one character at a time.

    • one year ago
  17. osanseviero Group Title
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    why are the results numbers?

    • one year ago
  18. e.mccormick Group Title
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    str(i) is not the same as str[i]

    • one year ago
  19. e.mccormick Group Title
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    ``` >>> s = "this is a test" >>> s[1] 'h' >>> i=1 >>> s[i] 'h' >>> s(i) Traceback (most recent call last): File "<interactive input>", line 1, in <module> TypeError: 'str' object is not callable ```

    • one year ago
  20. osanseviero Group Title
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    It never gives me an answer :/ s=raw_input("Enter a word: ") substring="" for i in range(len(s)-1): if s[i]<s[i+1]: substring=str(i) + str(i+1) if s[i]>=s[i+1]: substring="" print("Longest substring in alphabetical order is: " + str(substring))

    • one year ago
  21. e.mccormick Group Title
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    Like I said, you will need two buffers to hold strings. Also, you still have str(i). That is the numbers. You need s[i]. Also, this is how you turn multiple things into one but keep the first thing as part: ``` >>> a = 'abc' >>> b = 'def' >>> c = 'hij' >>> a 'abc' >>> a = a + b + c >>> a 'abcdefhij' >>> ```

    • one year ago
  22. osanseviero Group Title
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    I have two hours to finish this :/ Can you give me a push?

    • one year ago
  23. osanseviero Group Title
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    It throws me this :( string indices must be integers, not str

    • one year ago
  24. osanseviero Group Title
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    s=raw_input("Enter a word: ") substring="" output="" for i in range(len(s)-1): if s[i]<s[i+1]: substring=substring+s[i] if len(substring)>len(output): output=substring else: substring="" print output

    • one year ago
  25. osanseviero Group Title
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    Forget it, no more time. I still want to achieve this

    • one year ago
  26. thisSucks Group Title
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    @e.mccormick doen't leave any question unanswered

    • one year ago
  27. e.mccormick Group Title
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    Some possible flow of control issues.

    • one year ago
  28. osanseviero Group Title
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    Let me check this

    • one year ago
  29. e.mccormick Group Title
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    Forgot to put all the yes/no on that.

    • one year ago
  30. e.mccormick Group Title
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    • one year ago
  31. e.mccormick Group Title
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    I also realized that you need to test the last character in there somewhere, which is why that has another if in it.

    • one year ago
  32. osanseviero Group Title
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    which is the use of for i=0?

    • one year ago
  33. e.mccormick Group Title
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    It is a way of showing a for loop in a diagram.

    • one year ago
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